Fluid actuator with annular piston locking means



Aug. 20, 1968 SKELTON ET AL 3,397,620

FLUID ACTUATOR WITH ANNULAR PISTON LOCKING MEANS 2 Sheets-Sheet 1 Filed Oct.

INVENTORS D. M. SKELTON J E. SCH ULTZ R.A. BEWALDA, JR

D. M. SKELTON ET AL 3,397,620

Aug. 20, 1968 FLUID ACTUATOR WITH ANNULAR PISTON LOCKING MEANS 2 Sheets-Sheet 2 Filed Oct. 6, 1966 I 4 Z25 32 z E I 1 /Z M INVE NTORS D. M. S KELTON J E SCHULTZ R A. BEWALDAJR' United States Patent 3,397,620 FLUID ACTUATOR WITH ANNULAR PISTON LOCKING MEANS Darold M. Skelton, Brookfield, John E. Schultz, South Milwaukee, and Robert A. Bewalda, Jr., Cudahy, Wis., assignors, by mesne assignments, to Milwaukee Cylinder Corporation, Cudahy, Wis., a corporation of Wisconsin Filed Oct. 6, 1966, Ser. No. 584,818 1 Claim. (Cl. 92-24) ABSTRACT OF THE DISCLOSURE A pneumatic or hydraulically actuated cylinder and piston unit having piston locking means including a singular, annular piston located in the head of the cylinder, which piston is fluid-actuated for urging locking means into engagement with the piston of the cylinder.

This invention relates to improvements in pistons, and more particularly to a novel mechanism for releasably locking a pneumatic or hydraulically actuated piston in a raised position.

Pneumatic and hydraulic pistons have a number of uses in industry, including the continuous intermittent raising and lowering of machine tools or parts during manufacturing operations, and it is frequently desired to automatically temporarily halt such pistons in a raised position for a predetermined time interval during their operating cycles. The conventional manner of accomplishing this is to maintain a sufiicient quantity of air or fluid under pressure in the piston cylinder to keep the piston and its load in a raised position. Unfortunately, however, this creates a strain on the air or hydraulic fluid system, particularly when there is a heavy load on the piston, and is not entirely satisfactory for many applications. Moreover, in the event of a leak or failure in the power system the piston will he accidentally released, which can have disastrous results.

With the above in mind, the principal object of the present invention is to provide a novel automatic and releasable locking mechanism for pneumatic or hydraulic pistons which eliminates the necessity of utilizing air or fluid pressure to maintain the piston in a raised position, thereby facilitating the job of the power equpment and also promoting safety in the event of a leak or failure in the system.

A further object of the present invention is to provide a novel locking mechanism for pneumatic or hydraulic pistons which is simple and reliable in operation.

Still further objects of the present invention are to provide a new and improved piston locking mechanism which is relatively inexpensive in design and construction, which is rugged and durable in use, and which is otherwise particularly well adapted for its intended purpose.

With the above and other objects in view, which other objects and advantages will become apparent hereinafter, the invention comprises the novel locking mechanism for pneumatic or hydraulic pistons described in the following specification, and illustrated in the drawing, and any and all modifications or variations thereof as may come within the spirit of said invention and within the scope of the appended claim.

In the accompanying drawing, wherein there is illustrated one preferred embodiment of the invention, and wherein the same reference numerals designate the same parts in both of the views:

FIG. 1 is a side elevational and sectional view of the improved cylinder and piston assembly showing the piston in a lowered position; and

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FIG. 2 is a similar view showing the piston in its raised, locked position.

Referring now more particularly to the drawing, the numeral 10 designates a cylindrical piston housing and the numeral 11 designates a piston rod slidably carried within and projecting from the lower end of said cylinder, said piston rod having an enlarged head 12 on its upper portion which is closely movably fitted within said cylinder. Suitable sealing rings 13 are provided to ensure a tight, leakproof fit between said movable piston head 12 and the inner surface of the cylinder 10. Said piston head 12 is secured on the upper portion of the piston rod 11 by means of a nut member 14 which is threaded onto the end of said piston rod, and which nut member includes an upwardly-projecting portion 14 having a beveled annular groove 15 formed therein, the function of which will be hereinafter seen.

In FIG. 1 of the drawing the reciprocable piston rod 11 is shown in a lowered position, and in FIG. 2 said piston is shown in a fully elevated position at the top of its stroke, with the piston head 12 abutting against the end cap 16 on the upper end of the cylinder. Said cap 16 may be clampingly secured on the top of the piston cylinder by means of elongated rods 20 projecting upwardly from the cylinder base 23, or by other suitable retaining means.

It is to be understood that while the piston and cylinder structure illustrated in the drawing and hereinafter described is designed for use with a pneumatic power system it is also possible to utilize hydraulic fluid power, and the invention is not to be limited in this respect. Similarly, the positioning and mounting arrangement as well as many of the details of construction of the illustrated cylinder and piston assembly may be modified or altered for particular applications, and the invention is not to be confined to a unit identical in all respects to that shown and described herein. It is contemplated, for example, that in lieu of the unique nut member 14-14 the piston rod 11 could be formed with an integral upward extension having a groove therein similar to the groove 15 in said nut member, as well as numerous other modifications in the illustrated structure.

The cylinder cap 16 in the present invention is provided with a transverse central bore 17 designed to receive the upwardly projecting portion 14' of the piston nut 14 when the piston rod is in its raised position (FIG. 2), said bore being of substantially greater diameter than said nu-t member. Vertically movably carried within said bore 17 is a plug 18, and seated within and projecting upwardly from a pocket in said plug is a compression spring 22 which bears against :the bottom surface of a plate 19 secured on the outer face of the cap 16 by means of bolts or screws 21.

Encircling said plug 18 within the cylinder cap bore 17 is a rigid concentric collar 25 having an inwardly projecting lower section adapted to closely surround the lower portion of said plug, and also forming an annular shoulder 25' against which the enlarged head portion of said plug abuts when said plug is in its lowered position (FIG. 1). Formed in and around said collar 25 is a circumferential ring of closely spaced bores or ports 38, and movably mounted in each of said ports is a ball 27, said balls being larger in diameter than the thickness of said collar wall and being designed to protrude either inwardly or outwardly beyond said wall. In FIG. 1 of the drawing said balls 27, hereinafter referred. to as the locking balls, are shown projecting outwardly while in FIG. 2 they are illustrated in a position projecting radially inwardly within the cap bore 17, the function of which will be hereinafter seen. Said bores or ports 38 are tapered inwardly, as shown, to retain said locking balls therein, and a concentric ring unit 24 closely encircling the collar 25 pre- 3 vents said balls from escaping laterally outwardly of said collar.

Said ring unit 24 is adapted to move vertically relative to the rigid collar 25 against the action of a spring 26 mounted therebetween, and against the action of a plurality of equispaced springs 31 which bear against the underside of the top plate 19, said springs functioning to yieldably urge said ring unit 24 downwardly to the lowered position of FIG. 2. Sealing rings 28 provide a leakproof engagement between said movable ring unit 24 and said collar 25, as well as with the surface of the cap bore 17. Said ring unit 24 is also provided with a downwardly and inwardly beveled lower exterior face 24, and the inner face of said ring is provided with an annular cutout 36 which is designed to accommodate a portion of the locking balls 27 when said ring unit is in the raised position illustrated in FIG. 1, the upper surface of said cutout being beveled as shown.

Formed in the side of the cylinder cap 16 in the present invention is a radial tapped bore 32 which communicates with the central bore 17, and in the use of the invention an air -(or hydraulic fluid) hose is threaded into or otherwise connected to said bore to permit the introduction of air or other fluid under pressure into said cap, there also being suitable exhaust means. Desirably a radial exhaust bore 37 and duct 37 communicating with the interior of the cylinder are provided, and a needle valve (not shown) or the like is mounted within said bore 37 to control the fluid pressure and to thereby regulate the speed of the reciprocable piston 11 as it approaches the top of its stroke.

In the operation of the illustrated pneumatic piston assembly in a typical manufacturing operation an air inlet line (not shown) leading from a source of air or hydraulic fluid under pressure is connected to the lower portion of the cylinder 10 to provide power means for raising the piston, as is conventional in the art, and suitable release valve and return line means permit the descent of said piston and the load carried thereby. As hereinabove mentioned, the operating cycle can be automatically timed and controlled for the particular machining operation or other intended use of said piston.

In accordance with the present invention, as the piston rod 11 approaches the top of its stroke the upwardlyprojecting portion 14' of the piston nut 14 enters the lower end of the bore 17 in the cylinder cap and engages against the bottom of the movable plug 18, continued upward travel of said piston and nut pushing said plug 18 upwardly against the pressure of the spring 22. As said plug 18 moves upwardly to a position above the locking balls 27 said balls are free to shift laterally to an inwardly projecting position (FIG. 2), and when the piston and nut 14 reaches the top of its stroke the groove in said nut is aligned with said balls. Simultaneously, the freedom of said balls 27 to shift laterally inwardly permits the ring unit 24 to move downwardly to the lowered position illustrated in FIG. 2, the aforementioned springs 26 and 31 functioning to urge said ring unit 24 downwardly. The beveled nature of the cutout 36 in said ring unit acts as a wedge to force the locking balls 27 inwardly into the piston groove 15, and when said ring unit is in its lowered position the vertical inner face thereof bears against said balls 27 and maintains the same in position within said groove. Thus, with said balls 27 projecting into said piston groove 15 the piston is mechanically clamped against vertical movement and the air or fluid in the cylinder 10 can be exhausted, with the attendant advantages hereinabove enumerated.

When it is desired to release the piston 11 air under pressure is introduced into the cylinder cap 16 through the bore 32 and as said air flows into the cap it forcibly engages against the beveled annular face 24 of the ring unit 24 and urges said ring unit upwardly against the tension of the springs 26, 31. As said ring unit 24 moves upwardly the annular cutout portion 36 therein is brought into alignment with the locking balls 27 and said balls are free to shift to an outwardly projecting position, as shown in FIG. 1, the beveled nature of the piston groove wedging said balls outwardly as said piston bears downwardly thereon. Thus the piston 11 is free to descend and commence a new operating cycle.

When the piston and nut 14 move downwardly, as described, the spring-loaded plug 18 follows downwardly therewith and engages against the balls 27 to maintain said balls in their outwardly projecting or retracted position (FIG. 1), thereby ensuring that the locking mechanism is ready for the next upward stroke of the piston.

As hereinabove mentioned, the advantage of the present invention is that it makes it unnecessary to continuously employ air or fluid pressure in the cylinder in order to secure the piston at the top of its stroke, as is required with prior piston assemblies. Not only is said conventional method inetficient and a strain on the power equipment, but in the event of a leak or failure in the system the piston will be accidentally released, which can have serious and even disastrous results.

What we claim is:

1. A piston and cylinder assembly, comprising: an upright cylinder having a base end and a top end; a cap on the top of said cylinder, said cap having a central bore opening in the bottom thereof, and having a fluid inlet bore communicating with said central bore; a rigid, concentric collar mounted within said cap central bore and formnig an annular chamber therewith, said collar having a circumferenital ring of spaced, inwardly tapered ports therethrough; a locking ball mounted in each of said collar member ports, said balls being of a diameter greater than the width of said collar wall and being adapted to project either inwardly or outwardly therebeyond; a vertically movable annular piston slidable in said annular chamber, said annular piston having a downwardly and inwardly beveled outer face and having an annular cutout in its inner face provided with a beveled upper surface, said annular piston being movable from a raised position wherein said cutout is aligned with and adapted to accommodate a portion of said locking balls when the latter are in an outwardly pr0 jecting, retracted condition to a lowered position wherein the inner face of said annular piston bears against said balls and maintains the same in an inwardly projecting, locking condition; spring means yieldably urging said annular piston to a lowered position; a vertically movable plug extending downwardly in said cap central bore and closely movably fitted within said collar member, spring means yieldably urging said plug downwardly to a lowered position wherein the side of said plug engages said locking balls and maintains the same in an outwardly projecting, retracted condition, and wherein said balls retain said movable annular piston in its raised position; a reciprocable piston rod mounted coaxially within and extending downwardly from said cylinder, said rod having an enlarged piston head on its upper portion; an extension on said piston rod extending upwardly from said piston head and adapted to be projected upwardly into said cap central bore, and said rod extension having a beveled annular groove formed therein adjacent its upper end adapted to receive said locking balls when said balls are in their inwardly projecting condition; fluid power means for actuating said reciprocable piston rod, whereby as said piston rod approaches the top of its stroke said extension thereon will project into said cap central bore and push said movable plug upwardly therewith until the groove in said piston extension is aligned with said locking balls and the latter are caused to shift laterally by said spring loaded annular piston to a position wherein said balls project into said piston extension groove to mechanically lock said piston rod against downward movement, and with said annular piston in its lowered position; and means for introduc- 5 3 ing fluid under pressure into the fluid inlet bore in said cylinder cap to engage against the beveled face of said annular piston to force said annular piston upwardly to a raised position wherein said lockin balls are free to shift laterally outwardly to release said piston rod.

References Cited UNITED STATES PATENTS 2,360,535 10/1944 Ashton 9224 X 2,493,875 1/ 1950 Hunter 92-27 2,713,328 7/1955 DriSkel et a1. 92'24 6 Lieser 92-24 X Driskel et al 92-'24 X Powers et a1. 92-24 Lucien 92-15 X Ellis 91--45 X Ortman et al 92-85 X FOREIGN PATENTS Great Britain.

10 MARTIN P. SCHWADRON, Primary Examiner.

I. C. COHEN, Assistant Examiner. 

